Recent theorizing suggests that exposure to sophisticated or behaviorally complex messages (i.e., messages that reflect a concern with multiple goals) may enhance the cognitiue development of message recipients. Reasoning that persons attempt to accommodate their cognitive structuring of an environment to the level of complexity in that environment, it was hypothesized that persons exposed to behaviorally complex messages would form more differentiated impressions of the message source than would persons exposed to less complex messages. It was also hypothesized that persons with complex systems of interpersonal constructs would form more differentiated impressions of the message source. Further, because persons with complex systems of interpersonal constructs should better appreciate the richness of behaviorally complex messages, it was hypothesized that message complexity would exert the strongest effect on impression differentiation for those with high levels of cognitive complexity. Participants in the study (410 college students) read a conversation containing comforting messages representing one of three levels of behavioral complexity; they subsequently wrote impressions of the source of these messages and these impressions were scored for the number of attributes they contained. Interpersonal cognitive complexity was assessed with Crockett's (1965) Role Category Questionnaire. Consistent with hypotheses, main effects for behavioral complexity and cognitive complexity were observed on impression differentiation; in addition, the anticipated interaction between message complexity and cognitive complexity was observed.